A study consisting of a prospective and retrospective cohort in the ICU, ER and pulmonary department in a university hospital in Amsterdam and a teaching hospital in Alkmaar, the Netherlands.

The relationship between the oxygen saturation measured by pulse-oximetry and the arterial PaO2 is investigated in order to investigate which transcutaneous saturation values are safe when administering oxygen in relation to hyperopia and hypoxia.

This study consists of two parts a prospective and a retrospective part.

1. Prospective part: Patients in the ICU, the emergency room and the pulmonary function department of the VU university medical centre will be included. Arterial blood gas analysis is a tool often used to determine PaO2 in regular care. When an arterial blood gas analysis is performed for regular patient care, the corresponding SpO2 is measured. Information such as blood pressure, heart rate, amount of administered fluids and shock-related-parameters are obtained from the patient files. For the ICU patients capillary refill, acra temperature and the mottling scores are examined. The peripheral flow index and temperature index is measured. When more arterial blood gas samples are drawn over time in one patient, multiple datasets can be included per patient, as long as the samples are drawn two hours apart.
2. Retrospective part: Patients with a (suspected) pulmonary disease who underwent pulmonary function tests with arterial bloodgas sampling in the VU medical center and Medical Centre Alkmaar in the last 25 years. The PaO2 and corresponding SpO2 will be obtained from the test and parameters such as blood pressure, heart rate and administered oxygen will be retrieved from the databases with these test results.

Inclusion criteria for all inclusions:

• Age: 18>
• Requiring arterial bloodgas analysis

Exclusion criteria for all inclusions:

• Hyperbilirubinemia (>20 μmol/L)
• CO-Hb (>1,5%)
• MetHb (>1,5%)
• Unreliable pulsatile SpO2 curve

Additional inclusion criteria:

- Prospective, ICU - VUmc: On mechanical ventilation. Arterial line in place.

Additional exclusion criteria:

• Prospective, ICU - VUmc: On extracorporeal membrane oxygenation. Therapeutic hypothermia.
• Retrospective, Pulmonary function departments: Uncertainty whether SpO2 was measured exactly during arterial bloodgas sampling.

Prospective

• ICU - VUmc: Critically ill patients, requiring invasive monitoring
• Pulmonary function department - VUmc: Patients requiring a pulmonary function test with arterial bloodgas analysis.
• ER VUmc: Patients presented at the shockroom or patients in the general ER, requiring arterial bloodgas analysis.

Retrospective

- Pulmonary function departments: Patients who underwent a pulmonary function test with arterial bloodgas analysis in the last 25 years.